Conventionally, there have been air-conditioning apparatuses configured by connecting a plurality of use units via a refrigerant extension pipes to at least one heat source unit. Where there is abnormality in the operational state of such an air-conditioning apparatus, or in the case of periodical inspection, a worker visits the installation place and performs mending and repair of the malfunctioning parts. However, since an air-conditioning apparatus is composed of many parts, search for malfunctioning parts greatly relies on experiences or ability of the workers, and in many cases a prolonged time is required to identify the malfunctioning parts. In order to achieve an improved maintenance and service organization, it is essential to identify malfunctioning parts in a short time. Therefore, many methods have been developed so far for searching malfunctioning parts.
As such methods, a technique is disclosed that maintains a motor rotation speed at a constant value to yield the constant state of a refrigerant at the inlet and the outlet of the compressor, and maintains a constant rotation speed of an outdoor unit fan to achieve a constant degree of heat exchange at a condenser. This technique thereby calculates a refrigerant amount ratio accurately (see, for example, Patent Literature 1).
Further, a technique is disclosed that determines the amount of refrigerant within a refrigerant circuit by: stabilizing a flow rate of the refrigerant suctioned and discharged by a compressor by implementing a constant compressor rotation speed control; and controlling an indoor expansion valve to achieve a constant degree of superheating so that the amounts of refrigerant at the indoor heat exchanger and a gas refrigerant communication pipes become constant (for example, see Patent Literature 2).
Further, a technique is disclosed in which an indoor unit is connected to a branching unit having an electromagnetic expansion valve via each branching port of the branching unit, all indoor units drive in a heating operation, and correspondence between the pipes and wiring of the indoor units and branching units are detected by closing the electromagnetic expansion valves one by one (for example, see Patent Literature 3).